Tillerson was ousted barely four hours after he returned from an Africa mission and with no face-to-face conversation with the president, the latest casualty of an unruly White House that has seen multiple top officials depart in recent weeks. Citing the Iran nuclear deal and other issues, Trump said he and Tillerson were "not really thinking the same."

"We disagreed on things," Trump told reporters at the White House â€” a diplomatic take on a fractious relationship that included reports that Tillerson had privately called the president a "moron."

Appearing in the State Department briefing room for likely the last time, Tillerson's voice quavered as he described successes of his roughly one-year tenure: an economic pressure campaign on North Korea and a new Afghanistan plan.

"I will now return to private life, private citizen, a proud American, proud of the opportunity I've had to serve my country."

He did not mention Trump â€” other than to say that he'd spoken by phone to the president Tuesday while Trump was on Air Force One.

He said he would delegate all authority to Deputy Secretary John Sullivan, who will serve as acting secretary until Pompeo is confirmed. Tillerson will remain secretary in name until March 31, when he formally resigns his commission.

In an illustration of the gulf that has long separated Tillerson and Trump, the White House and the State Department vigorously disagreed about whether Tillerson had even been informed of his firing in advance.

Undersecretary of State Steve Goldstein and other State Department officials said Tuesday morning that Tillerson hadn't learned he was dismissed until he saw Trump's early-morning tweet, and hadn't discussed it directly with Trump. Goldstein said the former Exxon Mobil CEO was "unaware of the reason" he was fired and "had had every intention of staying."

Multiple White House officials said that Tillerson had been informed of the decision Friday, while he was in Ethiopia. One official said chief of staff John Kelly had called Tillerson on Friday and again on Saturday to warn him that Trump was about to take imminent action if he did not resign and that a replacement had already been identified. Tillerson canceled his entire schedule that Saturday in Ethiopia, with the State Department telling reporters he was sick.

All of the officials demanded anonymity because they weren't authorized to speak publicly.

"I think Rex will be much happier now," Trump said before flying to California.

Trump's change puts Pompeo, an ardent foe of the Iran nuclear deal, in charge of U.S. diplomacy as the president decides whether to withdraw the U.S. from the agreement. Trump faces another deadline in May to decide whether to remain in the Obama-era nuclear agreement that he campaigned aggressively against.

Tillerson has pushed Trump to remain in the agreement and had been pursuing a delicate strategy with European allies and others to try to improve or augment it to Trump's liking. The president mentioned differences over how to handle the Iran agreement, "so we were not really thinking the same."

The reshuffle also comes amid a dramatic diplomatic opening with North Korea, with Trump set to hold a historic meeting with leader Kim Jong Un in May. Pressuring North Korea with sanctions and other isolation measures had been a top Tillerson priority, and he had been one of the administration's more vocal advocates for holding talks in some form with the North. When Trump ultimately accepted Kim's invitation for a meeting, Tillerson was in Ethiopia, though he said he spoke with Trump at 2:30 a.m., shortly before it was announced.

Tillerson's departure adds to a period of intense turnover within Trump's administration that has alarmed those both in and out of the White House. Top economic adviser Gary Cohn announced his resignation last week, not long after communications director Hope Hicks and staff secretary Rob Porter both departed near the start of Trump's second year in office.

Speculation that Tillerson would be fired grew last fall with the reports of his "moron" insult, which the secretary state never personally denied.

The president said he was nominating the CIA's deputy director, Gina Haspel, to take over for Pompeo at the intelligence agency. If confirmed, Haspel would be the CIA's first female director

Pompeo, a former Republican congressman from Kansas, has been one of Trump's most loyal Cabinet members and quickly formed a close bond with the president, coming personally to the White House most days to deliver the President's Daily Briefing. Known for his blunt-talking style, Pompeo has already been confirmed by the Senate for his current role at the CIA, making it likely that he will be confirmed for the State Department role.

"He will do a fantastic job!" Trump tweeted.

But several Democrats quickly raised concerns about both Pompeo and Haspel, suggesting their confirmation hearings could be contentious. Sen. Ron Wyden of Oregon, a Senate Intelligence Committee, accused Pompeo of being insufficiently tough on Russia and said he'd "demonstrated a casual relationship to truth and principle."

Pompeo said he was "deeply grateful" to be nominated and looked "forward to guiding the world's finest diplomatic corps" if confirmed. He also praised Trump, saying, "His leadership has made America safer."

On Tillerson's plane trip back from Africa, he had told reporters he had cut short his mission by one night because he was exhausted after working most of the night both Friday on Saturday and falling ill.

At the White House, two officials said Trump wanted to have a new team in place ahead of an upcoming meeting with Kim, the North Korean leader.

One senior White House official said that when Trump made the decision to meet with Kim while Tillerson was in Africa, an aide asked if Tillerson should weigh in on the matter. Trump said there was no reason to consult him because no matter what the group decided, Tillerson would be against it, the official said.